1. Field of the Invention
The present invention relates to a video data transmitting and receiving apparatus and a video data transmitting and receiving method configured to receive a video data signal which is superimposed with particular information and inputted.
2. Description of Related Art
Generally, in bus transmission of video data, in addition to the video data and clocks, a horizontal synchronizing signal, a vertical synchronizing signal, a field phase signal or a data enable signal may be transmitted. As such video data transmission standards, SMPTE 274M, SMPTE 296M, ITU-R BT.656 and the like are known.
In such transmission standards, one pixel of the video data per clock is transmitted from an upper left pixel within a frame or a field, in raster scan order. Moreover, the horizontal and vertical synchronizing signals are asserted in synchronization with the raster scan.
Incidentally, in ISDB (Integrated Services Digital Broadcasting) standard, various video formats have been standardized. For example, for digital terrestrial broadcasting in Japan, there are 720×480i and 720×480p as SD (Standard Definition) formats, and there are 1920×1080i, 1440×1080i, 1280×720p, 1440×1080p and the like as HD (High Definition) formats.
A transmitter module for the bus transmission changes a period and a position of the synchronizing signal to be transmitted, or a position of a valid data area, depending on the video format. In other words, a transmission format in the video transmission depends on the video format. A receiver module can extract the synchronizing signal, thereby comprehend the transmission format, and perform processes depending on the transmission format, that is, a synchronization process, a valid data extraction process and the like depending on the video format.
Moreover, a method configured to separately transmit information on change of the valid data area which is associated with change of the video format of the video data to be transmitted, by using a transmission path different from a transmission path of the video data is also conceivable. In most cases, the transmitter module or an LSI including the transmitter module, and the receiver module or an LSI including the receiver module are connected to various buses, for example, a PCI bus or a processor bus, which is configured to control the transmitter module or the LSI including the transmitter module, and the receiver module or the LSI including the receiver module. In such cases, the information on the valid data area obtained in the transmitter module can be conveyed via the bus to the receiver module.
The receiver module can readily extract valid data by receiving such information on the valid data area. However, the information on the valid data area, and the video data are transmitted via different transmission paths. Therefore, even if there has been the change of the valid data area which is associated with the change of the video format, a setting for extraction of the valid data area may not be able to be changed simultaneously with the change of the format, and a normal video output may not be obtained immediately after the change of the video format.
Japanese Patent Application Laid-Open Publication No. 2007-13464 discloses an apparatus in which, if a display is switched from a first video signal to a second video signal, the first video signal is outputted to a displaying module also after the switching, until a signal process for the display of the second video signal is terminated. Thereby, the invention of Japanese Patent Application Laid-Open Publication No. 2007-13464 enables smooth video switching.
However, immediately after the change of the video format, the receiver module cannot obtain the video data immediately after the change of the video format. In other words, there is a problem that the receiver module cannot seamlessly obtain the video data immediately after the change of the video format of the video data from the transmitter module.